I'm afraid I couldn't disagree more. Everything else works fine and uses the *page cache*. We run 1000s of machines that do. You are getting confused between fs-cache and the kernels page cache.
Jim ----- Original Message ----- From: "Michael Black" <mdblac...@yahoo.com> To: "james vanns" <james.va...@framestore.com>, "General Discussion of SQLite Database" <sqlite-users@sqlite.org> Sent: Thursday, 7 February, 2013 1:47:03 PM Subject: RE: [sqlite] Strange eviction from Linux page cache Nothing to do with SQLite. NFS won't use cache by default. You have to mount it with the "fsc" option. https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/ht ml/Storage_Administration_Guide/fscachenfs.html -----Original Message----- From: sqlite-users-boun...@sqlite.org [mailto:sqlite-users-boun...@sqlite.org] On Behalf Of James Vanns Sent: Thursday, February 07, 2013 3:56 AM To: sqlite-users@sqlite.org Subject: [sqlite] Strange eviction from Linux page cache Hello list. I'd like to ask someone with more SQLite experience than me a simple question. First, some background; Distribution: Scientific Linux 6.3 Kernel: 2.6.32-279.9.1.el6.x86_64 SQLite version: 3.6.20 We have a single process that, given some data, does some processing and writes it all to a single SQLite DB file. This is a write-once process. When this task is finished, the file itself is marked as read only (0444). This file exists on an NFS share for multiple users to read - nothing further is ever written to it. The problem we're seeing is that when this DB file is read from (over NFS) none of the pages are cached (despite ~12GB free for page cache use) or at least immediately evicted. This is quite detrimental to performance because our resulting data files (SQLite DB files) are between 100 to 400 MB in size. We *want* it to be cached - the whole thing. The page cache would do this nicely for us and allow multiple processes on the same machine to share that data without any complication. I understand that SQLite implements it's own internal page cache but why, on a standard desktop machine, will it not use the page cache. Is there anyway of forcing it or bypassing the internal page cache in favour of the job that Linux already does? I cannot find any reference to O_DIRECT or madvise() or favdise() etc. in the code. The following PRAGMAs don't help either; PRAGMA writable_schema = OFF PRAGMA journal_mode = OFF PRAGMA synchronous = OFF PRAGMA cache_size = -<size of DB file in kbytes> Obviously that last one works - but only for a single process and for the lifetime of that process. We want the pages to reside in RAM afterwards. Anyone out there know how to correct this undesirable behaviour? Regards, Jim Vanns -- Jim Vanns Senior Software Developer Framestore _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users -- Jim Vanns Senior Software Developer Framestore _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
